Shell and Tube Heat Exchangers is most common type of heat exchanger in oil refineries and other large chemical processes, and is suited for higher-pressure applications. Shell Tubes Heat Exchanger are classified into fixed and Floating type Heat Exchangers. Shell and tube heat exchangers consist of a series of tubes. One set of these tubes contains the fluid that must be either heated or cooled. The second fluid runs over the tubes that are being heated or cooled so that it can either provide the heat or absorb the heat required.